So this has been driving me bonkers. I had everything dialed in, and then all of a sudden one of my print files started acting funny - it would print the first 50 or so layers fine, then above that it would barely extrude, leaving whispy towers of filament on top of the model.

So of course I checked - nozzle's clear. In fact, all I had to do was retract the filament, snip it, reinsert and it would be good to extrude again.

So, since it's a small thin part I thought that maybe the extruder was getting overworked by retracting and extruding all the time. So I disabled the retract - which made it worse! So I re-enabled it. Issue continued - first 50 layers or so, then no extrusion.

Then it started happening on all of my files. Now I can't print files that were fine just before.

I've also noticed that the cartridge has difficulty maintaining a consistent temperature - if I set it to 215, it goes up to 220, then down to 210 in a sine wave style pattern. It keeps overshooting and undershooting its target temperature. So, thinking that maybe the filament was getting soft and jamming up in the extruder motor, I dropped the target temperature to 205 so that it would only go up to 210 and down to like 190ish. Still no luck.

I've also noticed that the HBP is now cutting off its temperature returns at random intervals - sometimes it'll register, other times it will just show 0.

I've also tried cleaning the nozzle (it's fine), making sure the spool is free to rotate (it is).

Really hoping someone can help me solve these issues. This has been driving me nuts! Thanks!

The initial "above that it would barely extrude" suggests an extruder problem.

The "extruder was getting overworked by retracting and extruding" could point to a filament drive problem.

The "happening on all of my files" rules out a model geometry problem and definitely points to a mechanical or electrical issue.

None of those will have anything to do with the platform heater, so that's where I started.

When you see "it goes up to 220, then down to 210 in a sine wave style pattern", then you should run a PID auto-tune operation. Search the forum for details; it's been covered recently. Remember to store the new PID parameters when you're done.

You reported installing a new thermistor and cartridge in the hot end, then only the thermistor. Either of those may be different enough from the previous ones to require a retuning the PID loop controlling the temperature.

The "HBP is now cutting off its temperature returns at random intervals" is entirely different and suggests a problem with either the platform thermistor or its cable to the RAMBo.

So, do this in order:

0. Restore all your slicing settings to whatever they were before this mess started

1. Run a PID auto-tune to fix the hot end oscillation

1a. If the hot end temperature varies abruptly, then it's a bad hot end thermistor or its cable

3a. If the platform thermistor cable shows no problem, then you need a new platform thermistor. I don't know if they're available separately or if you're in for a whole new assembly.

You can get these separate you just have to ask for them as they are not listed on the site. (they were about $15 last time I ordered)

Depending on the age of your M2 yours may have a connector at the build plate for the thermistor but the new ones come wired completely with a single connector that plugs right into the Rambo board so you have to redo the wire harness. (the one I was sent was why too short for my kit M2 so it might be a good idea to measure your wire length and let them know exactly what you need.